Aircraft which can take off and land on the water have populated the skies for many years, since the dawn of powered aviation. Such aircraft have been considered seaplanes if unable also to take off and land on the ground, and amphibious if able to take off and land both on the ground and water. For purposes of this document, seaplanes are included in and considered a subcategory of amphibious aircraft, as amphibious aircraft which do not feature or have not been fitted with the sort of landing gear which allows takeoff and landing on the ground.
Amphibious aircraft have typically been of two general types. The first general type includes single fuselage designs in which the fuselage serves as flotation and usually includes appropriate hydrodynamic contouring. A prime example is the PBY Catalina multiengine aircraft in wide use in the mid-20th century. The second general type also has a single fuselage, but the fuselage is supported on floats or pontoons. Examples include any number of conventional aircraft which have been fitted with floats.
The single fuselage/hull amphibious aircraft have generally taken the form of larger, high-winged, multi-engine designs in an effort to position engine intakes and propeller arcs above water and spray. Lake Aircraft models, however, feature a single fuselage/hull design with high wing and a powerplant mounted on a strut above the fuselage. Other float design general aviation class aircraft avoid the spray issue by dimensioning the float struts of sufficient length to raise the fuselage and propeller arc of the typically forward-mounted engine above water line, spray being less of an issue since the engine is forward of the floats.
A significant issue with conventional float designs is the considerable additional aerodynamic drag created by the floats. That drag not only reduces range and airspeed, but it also creates additional moments of inertia about all of the yaw, pitch, and roll axes of the aircraft, and can thus degrade maneuverability of the aircraft. For smaller aircraft, the inventor has found that the designs featuring powerplants mounted too great a distance above the fuselage introduce stability issues, particularly on the water as well as in situations requiring radical power changes, as well as maneuverability issues which may arise as a result of the thrust axis being located an excessive distance above the center of gravity.
Twin fuselage aircraft have also been designed and used for various purposes, including the P38 Lightening, the P51 Mustang twin fuselage version and the B26 bomber designs widely used in World War II. Those designs typically offer an additional site at the forward end of a fuselage for a power plant and/or armament, together with additional stability at least about the roll axis. Similar designs include the single cockpit/twin tailboom aircraft such as the P61 Black Widow and the C119 Flying Boxcar.
One aspect of certain embodiments according to the present invention is to provide general aviation class amphibious aircraft which avoid any or all of aerodynamic drag and concomitant issues presented by pontoons and floats as well as structural, control and maneuverability issues presented by fuselage supported high engine designs, and which leverage the advantages of a twin fuselage, twin hull design in which the power plant is located aft and positioned advantageously with respect to water and spray.
Another aspect of certain embodiments according to the present invention is to provide amphibious aircraft in the general aviation class with any or all of increased range, speed and maneuverability, among other advantages, relative to conventional smaller float amphibious aircraft.
Another aspect of certain embodiments according to the present invention is to provide amphibious aircraft in the general aviation class which are eminently stable during take off, landing and taxiing phases on the water.
Other objects, features and advantages of the invention and embodiments thereof will become apparent with respect to the remainder of this document.